1. Field of the Invention
This invention relates to a wet type multiplate clutch for use in the automatic transmission of an automobile or the like, and more particularly to improvements in the positional relation between an oil groove for lubrication provided in a frictional material and the lubricant supply hole of a hub.
2. Related Background Art
FIG. 18 of the accompanying drawings is an axial cross-sectional view of a wet type multiplate clutch according to the prior art, and shows only the upper half thereof. A cylindrical retainer 104 is disposed on the inner periphery of a drum 105, and splines 104a are formed in the inner periphery of the retainer 104. Annular separator plates 103 are in meshing engagement with the splines 104a.
Respective friction plates 107 are disposed between adjacent ones of the separator plates 103, and teeth of the inner peripheral edges thereof are in meshing engagement with splines provided on the outer periphery of a hub 108. A flange 102 for receiving the friction plate 107 is disposed on the drum opening side end portion of the retainer 104, and is axially fixed by a snap ring 101. On the other hand, a piston 109 is provided on the closed side of the drum, and oil is introduced into an oil chamber 113 and pressure is created, whereby the piston is axially moved and brings each friction plate 107 and adjacent separator plate 103 into frictional engagement with each other.
An O-ring 106 which is a seal member is provided on the sliding surface of the piston 109. Lubricant supply holes 112 are formed in the hub 108 rotatable in the direction of the arrow so as to cool frictional materials 110 secured to the friction plates 107.
FIG. 19 of the accompanying drawings is a front view of a friction plate 107 meshing with the spline of the hub 108. FIG. 19 shows a quarter of the whole.
The hub 108 is formed with lubricant supply holes 112, and the frictional materials 110 are formed with through-oil grooves 111 extending through the inner and outer edges thereof and enhancing the cooling effect, and non-through-oil grooves 114 opening only to the inner peripheral edge and reducing the initial coefficient of dynamic friction during the frictional engagement thereof.
In the conventional example shown in FIG. 18, with regard to the second one from the piston side, the opening portion of the through-oil groove 111 is located at the front of the lubricant supply hole, but the opening portions of the through-oil grooves 111 of the other friction plates 107 are not opposed to the lubricant supply holes 112.
In recent years, the fact that drag torque is created by the viscosity of the lubricant used in the wet type multiplate clutch and results in a reduction in efficiency has posed problems. These problems cannot be solved by the conventional construction.